The following post has been edited, look at the end for my current solution to disable the nvidia geforce 210m on ul30vt
I can confirm that the nvidia card can be switched off on Ubuntu 12.04 LTS (32-bit). What I did was download the tarball from http://aur.archlinux.org/packages.php?ID=34499.
Then I compiled the source using:
Now 'sudo make install' didn't work, so instead I copied the 'nvidia_g210m_acpi.ko' manually. The exact path could be different for you, I used '/lib/modules/3.2.0-24-generic-pae/kernel/drivers/acpi/'
tar -zxvf nvidia-g210m-acpi.tar.gz
Now to confirm that the module loaded you can type 'dmesg|grep nvidia' and you should get a line that reads 'kill_nvidia: disabled the discrete graphics card'. Also my power usage decreased from 15-17 W to 10-12 W (at full screen brightness), and the fan stopped running when idle. Hope it works!
sudo cp nvidia_g210m_acpi.ko /lib/modules/3.2.0-24-generic-pae/kernel/drivers/acpi/
sudo depmod -a
sudo modprobe nvidia_g210m_acpi
Update: You should also consider removing the nvidia driver (sudo apt-get remove nvidia-current). This solved some serious lcd tearing issues I had, as well as making the desktop effects nicer (less pixelated).
Update2: I haven't found out how to load the module nvidia_g210m_acpi at startup. In ubuntu 10.04 I used /etc/rc.local, but if I do that in 12.04 the system hangs during boot. It also hangs if I use /etc/init/rc.conf or /etc/modules. Any other suggestions? At the moment I have to manually start the module ('sudo modprobe nvidia_g210m_acpi').
Update3: For some reason my computer has started crashing during suspend when the module nvidia_g210m_acpi is loaded. This was not a problem the first days after using this module - but now it is, so I guess this solution isn't optimal, and bumblebee (or ironhide) is probably a better alternative.
I have now stopped using the module (nvidia_g210m_acpi) since it broke suspend after some time. I've now switched to bumblebee, which seem to work very good. I installed bumblebee according to http://www.bumblebee-project.org/install.html, and then the nvidia card is automatically disabled if you don't want to use it specifically (which is done by launching an application with through the 'optirun' program). Power consumption is similar to loading the nvidia_g210m_acpi, and stays around 10W with screen brightness at 100% and otherwise idle.